Term used for video game sequels that are completely unrelated to the first one. Some infamous examples include Super Mario Bros 2, Zelda 2: The Adventure of Link, and Castlevania 2: Dracula's Curse. Games like these have different gameplay mechanics and sometimes completely different enemies and final bosses (Except for Castlevania 2 in this case).

For all 3 games mentioned, they have elements that are carried on to later games of their series.

Person A: Remember that game Super Mario Bros 2?
Person B: Yeah that game was a bastard child of the Super Mario series. Bowser wasn't even in the game.